Method of reproducing acoustic films



Jul 11, 1933. A. KAROLUS 1,917,306

METHOD OF REPRQDUCING ACOUSTIC FILMS Filed Jan. 28. 1930 INVENTOR AUGUSTKAROLUS BY Wk ATTORNEY on. Hence, the means here disclosed allowfrequency Patented July 11, 1933 UNITED STATES PATENT OFFICE.

AUGUST KAROLUS, OF LEIPZIG, GERMANY, ASSIGNOR TO RADIO CORPORATION OFAMERICA, A CORPORATION OF DELAWARE METHODOF' REPRODUCING ACOUSTIGFILMS rI Application filed January 28, 1930, Serial No.

The present invention is concerned with the photo-electric reproductionof acoustic films regardless of whether the latter have been made by theblackening or variable density or by the amplitude or variable areamethods so-called, and it discloses ways and means adapted to regulatethe intensity rela tions between the higher and the lower frequenciesand thereby the timbre and tonal qualities of the voice or music to bereproduced, in so far as it is possible to compensate to any desireddegree the decrease of the am plification or transmission factor forvery low frequencies. With this end 1n view the characteristic ofselenium "cells having, if desired, additions of other substances suchat tellurium, is utilized in the following manner: V

As shown by the single figure drawing, the

fono-film 1 is projected upon an adjustable slit 3 by means of a raypencil 2 which enlarges the photographic sound record or film optically.Such light as passes through sa d slit 3 impinges partly 1113011tllGPhOtO-BlGCtIlQ cell 6, for instance, a potassium cell system of theElster and Geitel type, while a regulable part of the light is shuntedlaterally through the shiftable'mirror 4 upon the selenium cell 5.Photo-electric cell 6 contains the positive electrode 7 and the negativeelectrode 8, the latter consisting, e. g., of patassium hydride. 9 withthe necessary Working potentials from taps taken off at difierent pointsand the path Y of the photo-electric current generated there;

in is made by way of the joint resistance 10 whose potential fall inwell-known manner acts upon the amplifier 11.

Now, while the photo-electric cell 6 inside the entire range or band offrequencies to be reproduced operates in a way free from distortion andinertia, selenium cell 5 furnishes potentials that will be so muchhigher, the lower the luminous frequency acting there- 1 l and thedistribution of the light over the Cells 6 and 5 are fed from a battery424,103, and Germany February 19, 192 9. 7

two cells. For instance, if the amplifier in case oftransformergcoupling exhibits a decrease'in amplification at the lowestfrequen cies,say, between and 100 cycles or if the loudspeaker connectedwith the scheme results in a fall in acoustic amplitude, then, as

the sensitiveness of cell 5 grows withdecreasing frequency, the drop inthei overall transmission factor can be compensated ad libitum.

By adding certain substances such as tel lurium to the selenium, it ispossible to advantageously affect the spectral characteristic as well asthe'frequency characteristic, and

also the conductivity and constancy of the cells in away advantageousfor carrying the present invent on into effect.

Having now described my invention, what.

I claim is 1. A system for regulating tonal qualities in'thereproduction of motion picture film sound records which includes alighttranslating element for converting fluctuating light intensitiesinto proportionate electric current"var1at1ons': free from distortionthroughout the frequency band to be reproduo-ed, and a second lighttranslating'element parallelly vconnected with said first named elementand having a sensitivity increasing with decreasing frequency.

2. A system for regulating tonal qualities in the reproduction ofrmotionpicture film sound records which in'cludes a light translating elementfor converting fluctuating light intensities into proportionate electriccurrent variations I free from distortion throughout the frequency bandto be repro duced,a second light translating element par-1 allellyconnected with said first named element and having a sensitivityincreasing with decreasing frequency, and means for simul- H taneously'exciting both of said elements by a fluctuating light ray'representativeof'the sound being reproduced.

3. Means for influencing and regulating the transmission. factor andtonal qualities for different frequencies in photoelectric reproductionof acoustic films which comprises two photoelectric cells, means fordistributing the light representative of the sound being produced in aregulable manner between said cells, one of said cells being of suchcharacteristics as to operate practically free from distortionthroughout the frequency band to be reproduced, and the other of saidcells being of such characteristics as to increase in sensitiveness asthe frequency decreases, and means for combining the current regulatedby said photo cells to actuate the sound reproducing system.

4. Means for influencing and regulating the transmission factor andtonal qualities for different frequencies in photoelectric reproductionof acoustic films which comprises two photoelectric cells, means fordistributing the light representative of the sound being produced in aregulable manner between said cells, one of said cells being of suchcharacteristics as to operate practically free from distortionthroughout the frequency band to be reproduced, and the other being aselenium cell having such characteristics as to increase insensitiveness as the frequency decreases,

a sound reproducing system, and means for combining the currentregulated by said photo cells to actuate the sound reproducing systom. 7a V 5. Means for influencing and regulating the transmission factor andtonal qualities: for different frequencies in photoelectric reproductionof acoustic films which comprises, two photoelectric cells, means fordistribut ing the light representative of thesound being produced in aregulable manner between two different cells, one of said cells being ofsuch characteristics asto operate practically free from distortionthroughout the fre-. quency band to be reproduced, and the other being aselenium cell containing tellurium having such characteristics as toincrease in sensitiveness as the frequency decreases, a soundreproducing system, and means for combining the current regulated bysaid photo cells to actuate the sound reproducing system. V

6. The method of regulating the quality of sounds reproduced fromamotion picture film which comprises converting variations in a lightbeam representativejof the sound being reproduced into a varyingelectrical current which varies in proportion to the variations of saidlight beam, converting a portlon of said varying light beam into asecond electrical current, the intensity of which variesdisproportionally with respect to the variations of said light beam, andcombining the currents thus produced to produce a current in whichthedesired frequencies are emphasized to compensate for the inherent lackof response of the reproducing equipment to such frequencies.

7. The method of regulating the quality of sounds reproduced from amotion picture film which comprises producing a Varying beam of lightrepresentative of the sound to be reproduced, converting variations ofsaid light beam into a varying electrical current varying in proportionto the variations of said light beam, converting a portion of saidvarying light beam into a second electrical current the intensity ofwhich varies disproportionally with respect to the variations of saidlight beam, and combining the currents thus produced to produce acurrent in which certain desired frequencies are emphaproduced into avarying electrical currentwhich varles 1n proportion to said variation,

converting a portion of said variations into a second electrical currentthe intensity of which varies disproportionally with respect to saidvariations, and combining the cur-' rents thus produced.

9, The method of regulating the quality of sounds reproduced from amotion picture film which comprises converting variations of a lightbeam which are representative of the sound being reproduced into avarying electrical current, which varies in proportion to the variationof said beam, and convert-I ing a portion of said varying light beaminto a second electrical current, the intensity of which variesdisproportionally with respect to the variations of said light beam,whereby a current is produced in which the desired frequencies areemphasized to compensate for the lack ofresponse of th ment to suchfrequencies.

AUGUST KARo Us;

ereproducing equip

